LET Performance Requirements Presenter: Richard Mewaldt RMewaldt@srl LET Performance Requirements Presenter: Richard Mewaldt RMewaldt@srl.caltech.edu 626-395-6612 xxxxxxx

Illustration of DE-Total Energy Particle Identification L1L2L3 Fe Fe O O C C 4He 4He 3He 3He H H Scatter plot of simulated pulse-heights from the L1 vs. L2 and the L2 vs. L3 detectors on LET illustrating particle tracks from H to Fe. The resolution and calibration of the LET system must be sufficient to resolve the tracks of these and other species and measure their kinetic energy.

Level-1 Science Requirements Flowdown From the STEREO Mission Requirements Document Program-Level Requirements for the Stereo Project Baseline Science Requirements: 3. Discover the mechanisms and sites of energetic particle acceleration in the low corona and the interplanetary medium The STEREO mission shall determine: Characterize distribution functions to an accuracy of ±10% for electrons and/or ions with energies typical of solar energetic particle populations. Determine the location of particle acceleration in the low corona to within 300,000 km in radius and in interplanetary space to within 20°in total longitude. Requirements on LET (from the Level-1 Requirements Document): Shall measure SEP ion fluxes, spectra, and composition in two oppositely directed 100 x 30 deg or better FOVs, covering the energy range from 3 - 25 MeV/nuc for C to Fe ions, 1.5 to 13 MeV/nuc for He, and 1.5 - 3 MeV for H. The mass resolution shall be better than 0.35 amu for 3He and 4He. Time resolution shall be 1 minute for H and He Beacon data, and 15 minutes otherwise. Shall handle at least 1000 events/sec.

(from the IMPACT Performance Specification Document, Rev H) Specific LET Performance Requirements (from the IMPACT Performance Specification Document, Rev H) Description Requirement Goal Capability Verification Field of View 2 oppositely directed 100°x30° fans 2 oppositely directed 130°x30° fans 2 oppositely directed 133°x30° fans Geometrical analysis; lab detector mapping Energy Range (MeV/nuc) H: 1.5 - 3 He: 1.5 - 13 O: 3 - 25 Fe: 3 - 50 H: 1.4 - 6 He: 1.4 - 13 O: 2.5 - 25 Fe: 2.5 - 50 H: 1.2 - 10 He: 1.2 - 13 O: 2.3 - 33 Fe: 2 - 56 Pulser, proton, a-particle calibrate; detector maps; particle accelerator Geometry Factor (cm2sr) H, He: 0.9 6≤Z≤26: 4.5 Geometric analysis Element Resolution Resolve H, He, C, N, O, Ne, Mg, Si, Fe Also resolve Na, Al, S, Ar, Ca H, He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni Detector thickness maps, Monte Carlo analysis, particle accelerator

Specific LET Performance Requirements - continued Description Requirement Goal Capability Verification 3He, 4He Mass Resolution ≤ 0.35 amu ≤ 0.25 amu TBD -particle and pulser calibrations L1 Noise ≤ 90 keV rms ≤ 50 keV rms for proton detection to 6 MeV and m(4He) ≤ 0.25 amu Expect ~30 keV rms Pulser calibrations L1 thickness uniformity T ≤ 0.6 m rms for 3He identification T ≤ 0.3 m rms T ≈ 0.3 to 0.6 m rms in prototype devices (tbd) a-particle thickness maps Energy Resolution Dist. Funct’s accurate to 10% 1% <3%; dep. on L1, L2 thick knowledge Pulser, a-particle calibrations; particle accelerator Maximum Event Rate 1000 per sec 5000 per sec Bench tests with pulser and sources,

Specific LET Performance Requirements - continued Description Requirement Goal Capability Verification Energy Binning 6 intervals for Z ≥ 2; 3 for H 8 intervals per species for Z ≥ 2; 4 for H 10-12 intervals for Z ≥ 2; 8 for H Pulser, a-particle calibrations; Monte Carlo simulations; particle accelerator Species Binning H, 3He, 4He, C, N, O, Ne, Mg, Si, Fe Also identify S, Ar, Ca H, 3He, 4He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni Time Resolution 1-min H, He, Z ≥ 6; Telem. 1 hi-priority event/s 1-min H, He; 15-min Z ≥ 6; Telemeter 4 hi- priority events/s Z ≥ 6; Telem. 4-5 hi-priority events/s Pulser, a-particle calibrations; and particle accelerator Beacon Telemetry 1-min for H, He, Z ≥ 6 Pulser, a-particles, particle accelerator

Effect of Detector Thickness Variations on 3Heand 4He Mass Resolution

Simulation of LET Response Including all Important Contributions to the Charge and Mass Resolution L1L2L3 Fe Fe O O C C 4He 4He 3He 3He H H These simulations include the effects of Landau fluctuations as well as variations in the angle of incidence and detector-thickness uniformity (sT = 0.5 microns in L1, L2). All key species are resolved. Note that incidence-angle and detector-thickness corrections will be made onboard.